High Speed Transmission Equipment
Component Selection
The P2300SC MC SIDACtor device and the F1250T TeleLink fuse were chosen because
both components meet GR 1089 surge immunity requirements without the use of additional
series resistance. The P2300SC MC voltage rating was selected to ensure loop powering
up to 190 V. For loop powering greater than 190 V, consider the P2600SC MC. The
P0080SA MC SIDACtor device was chosen to eliminate any sneak voltages that may
appear below the voltage rating of the P2300SC MC.
ISDN Circuit Protection
Integrated Services Digital Network (ISDN) circuits require protection at the Network
Termination Layer 1 (NT1) U-interface and at the Terminating Equipment (TE) or
Terminating Adapter (TA) S/T interface. Signal levels at the U-interface are typically ±2.5 V;
however, with sealing currents and maintenance loop test (MLT) procedures, voltages
approaching 150 V rms can occur. (Figure 3.11)
Terminal
Adapter
Terminal
Non-ISDN
T
ISDN Compliant
Central Office Switching
System
Network
Termination
Layer 1
POTS
TA
Terminal Equipment
(ISDN
NT1
CO
Compliant)
B1
T
T
B2
U
TE
ISDN DSL
2-Wire,
160 kbps
2B1Q 2.5 V
Reference
D
B1
S
B2
TE
TA
D
NT2
PBX
ISDN Terminal
S
T Reference
4-Wire
S Reference, 4-Wire
Figure 3.11 ISDN Overview
Protection Circuitry
Longitudinal protection was not used at either the U- or the TA/TE-interface due to the
absence of an earth-to-ground connection. (Figure 3.12) At the U-interface, the
P2600SC MC SIDACtor device and F1250T TeleLink fuse provide metallic protection, while
the TA/TE-interface uses the P0640SC MC SIDACtor device and F1250T TeleLink fuse.
Figure 3.12 also shows interfaces not isolated from earth ground.
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SIDACtor Data Book and Design Guide
®
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